And here
http://www.freewebs.com/heroquestrevised/downloads.htm

and here
http://www.boardgamegeek.com/image/338403?size=original

There is of course always products like hirst arts for building a 3d floor plan but finding a hi res image and a good printer is just as good.

You could also trace up the grid onto foam core or a large painting canvas and paint one from scratch though even I am not so crazy as to paint flat terrain.

I was also thinking it would be neat, although heavy to use small tiles like you can find in most craft shops, then you could you use different coloured grout (caulking) to show where the walls and rooms are. This would be particularly nice built into a table though somewhat limited in use (unless you make it double as a chess board.)

Rather than painting the game pieces, my planned customization is to bring in metal models. For instance, I’m buying a variety of cheap skeletons from Mega Miniatures to replace the one skeleton pose. I’m also using the HeroQuest board and furniture for use in Song of Blades and Heroes games.

the problem with the one box game is they are a bubble market and ultimately not a good source of on going revenue.

GW’s Specialist games site is a great place to pick up the rules for the best one box games, the components can often be readily constructed, I have built a set of spacehulk tiles, 2 bloodbowl boards and a poop load of converted teams (still WIP). A little research is all thats needed. Check the forums and you can probably find pics of the above.